1. Field of the Invention
This invention relates to an image recording apparatus having a heated fixing device used in a facsimile machine, a copier, a printer of a multifunction printing apparatus. This invention more specifically relates to an image recording apparatus in which it is possible to change the temperature of the fixing roller heater for saving electric power in a multifunction device.
2. Discussion of the Background
In general, an electro-photographic image recording apparatus is used in a facsimile machine, a copier or other printing apparatus. The image recording apparatus has a heated roller for fixing a toner image on recording paper. That is to say, it supplies electric power to the heated fixing roller and raises the temperature thereof to the fixing temperature. The heated roller then fixes the toner image on the paper.
In order to properly fix the toner image on the paper, it is necessary to hold the temperature at the heated roller at the fixing temperature. However, holding the fixing heated roller at the temperature when not performing a fixing operation consumes unnecessary electric power and raises the temperature of the apparatus. Therefore, in a conventional system, the image recording apparatus holds the fixing roller at a preliminary temperature which is lower than the fixing temperature, starts to raise the fixing roller temperature to the fixing temperature before fixing, and is set to the fixing temperature when fixing. For example, in the case of a facsimile apparatus, the temperature of the fixing roller begins rising at the time of detecting a ring signal.
In a copier shown in the patent specification of Japanese patent application laid-open (KOKAI) No. 1-284886, the temperature of the heated roller is ordinarily set to a low temperature. The temperature of the fixing roller is set to a higher temperature upon detection of opening the cover of the glass platen. A predetermined time after copying, the heated roller used for fixing is set to a low temperature.
However, the above mentioned technique of controlling the fixing temperature in a conventional copier is not effective in a facsimile machine because the roller temperature starts to rise from the preliminary temperature to the fixing temperature when the ring signal is detected. Therefore, the conventional technique shown in the patent specification of Japanese laid-open patent application (KOKAI) 1-284886 is only effective in a copier in which the fixing temperature is raised upon opening the cover and setting a sheet of paper on the glass platen.